1. Field of the Invention
This invention relates to an apparatus for detecting ophthalmic diseases in a patient's eye, and more particularly to an improvement in the alignment capability of an apparatus used in detecting ophthalmic diseases in which laser light is radiated via an optical system at one spot in the camera oculi of the patient's eye, particularly in the anterior chamber thereof, and the laser light scattered therefrom is analyzed to measure the protein concentration for ophthalmic disease detection in the camera oculi.
2. Description of the Prior Art
The camera oculi is comprised of the camera oculi anterior (anterior chamber) and the camera oculi posterior (posterior chamber). The camera oculi anterior is defined by a space surrounded by the rear surface of the cornea, a part of ciliary body, iris, and the front surface of the crystalline lens, while the camera oculi posterior is defined by a space surrounded by the rear surface of the iris, inner surface of the ciliary body, and front surface of the crystalline lens. The camera oculi is filled with transparent humor aqueous, which has chemical and physical characteristics different from lymphatic liquid and is closely related to the metabolism of the cornea or crystalline lens. The humor aqueous contains proteins which increase causing the camera oculi to be turbid when it becomes inflamed.
In this respect, the measurement of protein concentration in the camera oculi of the patient's eye is of great importance in determining whether the camera oculi is inflamed, that is, whether a blood-aqueous barrier is functioning normally or not.
To measure the protein concentration in the camera oculi, a slit lamp microscope is very often used to determine the turbidity by grading via naked eyes. This is, however, disadvantageous because the diagnosis depends upon the judgement of the person who performs the measurement.
On the other hand, a photographic measuring method has been developed to make a quantitative measurement of the protein concentration. This method is, however, too complicated to analyze, thus making it very difficult to apply in a clinical examination.
To overcome this problem, an apparatus for detecting ophthalmic diseases has been proposed which includes means for focusing a laser beam at a selected spot in the camera oculi of an eye. In the apparatus, the light scattered from the eye is photoelectrically detected and converted into an electrical signal which is subsequently used to determine the protein concentration essential to ophthalmic disease detection in the camera oculi of the patient's eye. See, for example, Japanese Patent Laying-open No. 120834/87.
In order to increase the reliability of the measured data obtained using this type of ophthalmic disease detection apparatus, it is necessary that the measurements are always precisely made on the same part of the eye, which in, turn requires prior positional alignment of the patient's eye with the laser beam projector, and light-receiving means.
To achieve this type of alignment, conventional ophthalmic disease detection apparatuses have been provided with special index means. This makes the apparatus complex, however, because such means requires the use of an optical alignment system and the like, raising the manufacturing cost of the overall apparatus.